Image display device, image display system, and image display method

ABSTRACT

An image display device comprises a first control part, a first storage, and a display part. The first storage holds rendering elements, each of which includes a combination of rendering target information and rendering setting information, and a priority order assigned to each rendering element. The rendering target information includes data identification information which designates three-dimensional data of a rendering target and mask information which designates a rendering target area. The rendering setting information includes information which designates a two-dimensional image rendering method and rendering parameter. The first control part determines, based on the rendering setting information and the mask information, whether executing priority processing is necessary. If it is determined that it is necessary to execute the priority processing, either the mask information or the rendering parameter is modified, and a two-dimensional image is rendered based on the rendering elements whereupon the priority processing is executed.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP2011-123169 filed on Jun. 1, 2011, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

This invention relates to rendering a medical image, and moreparticularly, to a setting, saving, and reusing technology for renderinga medical image with the use of three-dimensional data collected by amedical imaging machine such as a magnetic resonance imaging (MRI)machine (nuclear magnetic resonance image diagnostic machine) or acomputed tomography (CT) machine.

The sophistication in the function of medical imaging machines such asMRI machines and CT machines in recent years has made collectingsectional images in large quantity possible. Medical image displaydevices, too, have been sophisticated in function, which has broughtabout an increase in speed and precision in the generation ofthree-dimensional data from sectional images, the rendering of a medicalimage from the three-dimensional data, and image processing on themedical image.

When interpreting a medical image (namely, making a diagnosis based on amedical image), selecting an appropriate method of rendering a medicalimage and adjusting a rendering parameter properly are necessary inorder to facilitate the identification of a focus site. Executing thisprocessing efficiently requires formulating information about the methodof rendering and the rendering parameter (hereinafter referred to asrendering settings) into a pattern, and saving and reusing the settingspattern. It is also requested to improve the ease of understanding of amedical image and the precision of medical image interpretation bycombining a plurality of rendering settings patterns flexibly and thusrendering a compositive medical image.

With regard to reusing a rendering settings pattern, Japanese PatentApplication Laid-open No. 2001-291090 proposes a three-dimensional imagedisplay device that facilitates the pattern formulation and reproductionof image processing for creating a three-dimensional image, imagediagnosis based on the three-dimensional image, treatment planning, andthe like.

As a method of rendering an image by combining a plurality of renderingsettings patterns, Japanese Patent Application Laid-open No. 2008-119252proposes a method in which a plurality of display characteristics curvesindependent of one another are set to a part of an image that is withinan observation target area, and are reflected at once. Japanese PatentApplication Laid-open No. 2007-135843 proposes a method of generatingand displaying an image in an area of interest and in other areas forwhich different rendering methods are used.

SUMMARY OF THE INVENTION

Formulating typical rendering settings into a pattern and reusing thepattern is one way to efficiently render a medical image with the use ofthree-dimensional data. However, there is a demand for being able to useonly a part of a rendering settings pattern to suit the purpose ofmedical image interpretation and the characteristics of the subject,instead of using the rendering settings pattern as it is, and togenerate a compositive medical image by combining a plurality of piecesof three-dimensional data or a plurality of rendering settings patterns.

In addition, when a compositive medical image is rendered by combining aplurality of pieces of three-dimensional data or a plurality ofrendering settings patterns, rendering all simultaneously is not alwayspossible, depending on the method of rendering and the positionalrelation of rendering target areas, and executing some priorityprocessing with respect to rendering target areas or rendering settingspatterns is required.

The conventional technologies described above cannot meet all of theserequests.

According to this invention, there is provided an image display device,comprising: a first control part; a first storage; and a display part,wherein the first storage holds a plurality of rendering elements eachof which comprises a combination of rendering target information, whichspecifies a rendering target, and rendering settings information, whichis referred to when the rendering target is rendered, and holds a placein priority order assigned to each of the plurality of renderingelements, wherein the rendering target information comprises dataidentification information for specifying three-dimensional arrangementof signal values which are rendering targets, and mask information forspecifying a rendering target area out of the three-dimensional signalvalue arrangement, wherein the rendering settings information comprisesinformation for specifying a method of rendering a two-dimensional imagebased on the three-dimensional signal value arrangement, and informationfor specifying a rendering parameter to be applied to the renderingmethod, wherein the first control part is configured to: determine,based on the rendering settings information and the mask information,whether or not priority processing in which one of the mask informationor the rendering parameter is modified needs to be executed; modify,when it is determined that the priority processing needs to be executed,the one of the mask information or the rendering parameter; and render atwo-dimensional image based on the plurality of rendering elements thatcomprise the modified one of the mask information or the renderingparameter, and wherein the display part displays the two-dimensionalimage rendered.

According to one embodiment of this invention, the medical image basedon the three-dimensional data can be displayed efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an outline of the configurationsof a medical image display device and medical information managementserver according to an embodiment of this invention.

FIG. 2A is a diagram illustrating the data structure of renderingsettings according to the embodiment of this invention.

FIG. 2B is a diagram illustrating the data structure of a renderingelement according to the embodiment of this invention.

FIG. 3A is a diagram illustrating the data structure of compositiverendering settings according to the embodiment of this invention.

FIG. 3B is a diagram illustrating the data structure of a compositiverendering element according to the embodiment of this invention.

FIG. 4 is a flow chart illustrating processing for interpreting amedical image according to the embodiment of this invention.

FIG. 5 is a diagram illustrating an example of a screen that isdisplayed by a display part according to the embodiment of thisinvention.

FIG. 6 is a flow chart illustrating steps of priority processing of acompositive rendering element according to the embodiment of thisinvention.

FIG. 7 is a flow chart illustrating a selection step of the priorityprocessing according to the embodiment of this invention.

FIG. 8A is a diagram illustrating two mask areas according to theembodiment of this invention that are not on the same projection ray.

FIG. 8B is a diagram illustrating two mask areas according to theembodiment of this invention that are on the same ray.

FIG. 8C is a diagram illustrating two mask areas according to theembodiment of this invention that overlap each other.

FIG. 9A is a diagram illustrating extended area excluding processingaccording to the embodiment of this invention.

FIG. 9B is a diagram illustrating area excluding processing according tothe embodiment of this invention.

FIG. 10 is a diagram illustrating processing of integrating opacitycurves according to the embodiment of this invention.

FIG. 11A is a diagram showing a state in which two overlapping maskareas are projected onto a two-dimensional image according to theembodiment of this invention.

FIG. 11B is a diagram showing a state in which two mask areas processedby the extended area excluding processing are projected onto atwo-dimensional image according to the embodiment of this invention.

FIG. 11C is a diagram showing a state in which only mask areas ofrendering elements low in priority order that have been processed by theextended area excluding processing are projected onto a two-dimensionalimage according to the embodiment of this invention.

FIG. 11D is a diagram showing a state in which only mask areas ofrendering elements low in priority order are projected onto atwo-dimensional image, without executing the priority processing,according to the embodiment of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A medical image display device and a medical information managementserver are described below with reference to the accompanying drawingsas an embodiment of this invention.

The configurations of the medical image display device and medicalinformation management server according to this embodiment are describedfirst with reference to FIG. 1.

A medical imaging machine 21 such as an MRI machine or a CT machinecollects sectional images (i.e., images made from signal values on crosssections) by image pickup, and transmits the images to a medicalinformation management server 15 via a network 20. The network 20 maybe, for example, an intranet of a hospital, a testing facility, or thelike, or the Internet.

A medical image display device 1 is a computer device that is coupled tothe medical information management server 15 to display an image such asa medical image generated by the medical imaging machine 21 by pickingup a sectional image, or by rendering based on three-dimensional datathat is constructed from a sectional image, so that a user can interpretthe medical image or input diagnosis information. The medical imagedisplay device 1 includes, for example, a central processing unit (CPU),a memory, a read only memory (ROM), a hard disk drive (HDD), aninput/output interface, a liquid crystal display (LCD), a keyboard, anda mouse.

The medical image display device 1 includes an input part 2, whichprocesses an input from the user, a display part 3, which keeps a screenfor displaying a medical image, a communication part 4, whichtransmits/receives information to/from the medical informationmanagement server 15 and an intra-hospital information system 22, a listmanagement part 6, which manages a list of medical image interpretationorders, a medical information list, a user list, and the like, arendering control part 7, which manages information related to renderingand executes priority processing, a rendering processing part 8, whichexecutes processing of converting a sectional image andthree-dimensional data, and renders, a display control part 9, whichexerts display-related control such as managing the position of anelement displayed on the screen, and a storage 10, which temporarilysaves a medical image, rendering settings, diagnosis information, andthe like. In the example of FIG. 1, the list management part 6, therendering control part 7, the rendering processing part 8, and thedisplay control part 9 are part of a control part 5. The control part 5is implemented by, for example, by the CPU by executing a program thatis stored in the memory. Therefore, processing executed by the controlpart 5 (i.e., the list management part 6, the rendering control part 7,the rendering processing part 8, or the display control part 9) in thefollowing description is actually executed by the CPU followinginstructions of a program that is stored in the memory.

The medical image display device 1 may be a device whose main purpose isto enable one to view a medical image and diagnosis information, anddoes not include enabling one to interpret a medical image.

The medical information management server 15 is a Picture Archiving andCommunication System (PACS: medical image diagnosis assisting system)server, and manages medical information such as a medical image,diagnosis information, and information about a patient. The medicalinformation management server 15 includes a control part 16, acommunication part 17, and a storage 18.

The control part 16 executes storing processing in which data receivedby the communication part 17 is stored in a database provided in thestorage 18, retrieval processing in which data requested by a datarequest from the medical image display device 1 is obtained from adatabase provided in the storage 18, and the like. The control part 16is implemented by, for example, a CPU and a memory.

The communication part 17 transmits/receives data to/from the medicalimage display device 1, the medical imaging machine 21, and theintra-hospital information system 22, which manages patient information,test information, accounting information, and other types ofinformation.

The storage 18 is provided with a database for accumulating sectionalimages collected from the medical imaging machine 21, medical imagesgenerated by the medical image display device 1, rendering settings,diagnosis information, reports or similar types of information,information about patients obtained from the intra-hospital informationsystem 22, and the like. The storage 18 is implemented by, for example,an HDD. The medical information management server 15 used may have thestorage 18 that is provided with a database where all the pieces ofinformation listed above are accumulated, or a plurality of medicalinformation management servers 15 each having the storage 18 that isprovided with a database where only particular information isaccumulated may be used in cooperation with one another. Alternatively,the intra-hospital information system 22 that has an equivalent databasemay be used in cooperation with the medical information managementserver 15.

A configuration example of information about the rendering of a medicalimage is described next with reference to FIG. 2A to FIG. 3B.

Rendering settings 30 illustrated in FIG. 2A are information made up ofa rendering method 31 and a rendering parameter 32.

The rendering method 31 is information for identifying the method ofdisplaying a sectional image, or the method of performing projectionprocessing on three-dimensional data. Concrete examples of how asectional image is displayed include a method in which a sectional imageobtained from the medical imaging machine 21 is displayed, and a methodin which an arbitrary sectional image by Multi-Planar Reconstruction(MPR) is displayed. The projection processing of three-dimensional datais, to give a more detailed description, processing of projecting animage onto a two-dimensional screen based on the three-dimensionalarrangement of signal values that are constructed from sectional imagesobtained by the medical imaging machine 21 (e.g., CT values). Examplesof how this projection processing is executed include volume rendering(VR), surface rendering (SR), Maximum Intensity Projection (MIP),Minimum Intensity Projection (MinIP), and virtual endoscopy (VE). Thefollowing description of this embodiment deals with a rendering methodin which the projection processing is performed on three-dimensionaldata. However, this invention is also applicable to a case where therendering method used is a method in which a sectional image isdisplayed, and the rendering method 31 in that case contains informationfor identifying the method of displaying a sectional image.

The rendering parameter 32 is a parameter applied in order to display animage based on two-dimensional data that is generated by the renderingmethod described above. Specifically, the rendering parameter 32includes a target value range 33, and other parameters 34 related to therendering method 31.

The target value range 33 limits the range of signal values to which theother parameters 34 are applied with respect to the range of signalvalues measured by the medical imaging machine 21. For instance, therange of CT values (signal values measured by a CT machine) is about−2,000 to +4,000 in general and, in the case of setting the renderingparameter 32 for brains, a signal value range of about 60 to 90 isspecified as the target value range 33. The other parameters 34 are notapplied to signal values outside the specified range.

The other parameters 34 include, when the rendering method 31 is VR, forexample, the window level, the window width, an opacity curve (namely,opacity allocation and color allocation to signal values), light sourceinformation, a view point in a three-dimensional space, and the like.

The rendering settings 30 are information that does not depend on aparticular piece of three-dimensional data. Specifically, the renderingsettings 30 that have been used to render an image from a piece ofthree-dimensional data can be reused to render a similar image from anyother piece of three-dimensional data. The storage 18 or the like maystore a plurality of rendering settings patterns 30 in the form ofcombinations of various rendering methods 31 and various renderingparameters 32.

A rendering element 35 illustrated in FIG. 2B is a combination of arendering target 36 and the rendering settings 30. The rendering target36 is information for specifying a target to which the renderingsettings 30 are applied (namely, the target of the rendering based onthe rendering settings 30), and includes a three-dimensional data name37 and a mask name 38.

The three-dimensional data name 37 is information for identifyingthree-dimensional data (namely, the three-dimensional arrangement ofsignal values), and a piece of three-dimensional data to which therendering settings 30 are applied is specified by this information.

A mask is information for specifying a rendering target area within athree-dimensional space to which three-dimensional data belongs, andcontains, for each voxel (a coordinate grid point in a three-dimensionalspace) of the three dimensional data, binary data that indicates whetheror not the voxel is a rendering target. The information volumes ofthree-dimensional data and a mask are large, which is why the renderingtarget 36 in this embodiment includes only names that are keys forcalling three-dimensional data and a mask (i.e., a three-dimensionaldata name 37 and a mask name 38). However, the rendering target 36 mayinclude three-dimensional data and mask data themselves.

The rendering element 35 is information about a particular piece ofthree-dimensional data, and is therefore used to reproduce renderingrelated to the particular piece of three-dimensional data, instead ofbeing reused for another piece of three-dimensional data. The renderingelement 35 may also be configured by allocating the rendering target 36to the rendering settings 30.

The rendering settings 30 and the rendering element 35 are managed bythe rendering control part 7, and the rendering processing part 8executes rendering processing with the use of the rendering element 35.The rendering settings 30 and the rendering element 35 are saved by therendering control part 7 in the storage 10 of the medical image displaydevice 1, or the storage 18 of the medical information management server15, to be called as the need arises and used as they are, or with amodification.

A compositive medical image can be generated from a set created bycombining a plurality of rendering settings patterns 30, or a setcreated by combining a plurality of rendering elements 35. Compositiverendering settings 40 which are a set created by combining a pluralityof rendering settings patterns 30 are illustrated in FIG. 3A. Acompositive rendering element 43 which is a set created by combining aplurality of rendering elements 35 is illustrated in FIG. 3B. Acompositive medical image is an image rendered in a state where aplurality of rendering settings patterns 30 or rendering targets 36 arepresent. For instance, using a different rendering settings pattern foreach piece of three-dimensional data or for each specific area improvesthe ease of understanding and the precision of medical imageinterpretation.

The compositive rendering settings 40 are, similarly to the renderingsettings 30, information that does not depend on a particular piece ofdata and can therefore be reused for an arbitrary piece of data. Thecompositive rendering element 43 can be, similarly to the renderingelement 35, used to reproduce the rendering of an image. The compositiverendering element 43 may also be configured by setting the renderingtarget 36 to each rendering settings pattern 30 that is included in thecompositive rendering settings 40.

Rendering processing is accomplished by creating a two-dimensionalmedical image from three-dimensional data through projection. For thatreason, when mask areas that are specified by a plurality of renderingelements 35 included in the compositive rendering element 43 overlap ona projection ray and the rendering settings 30 in one mask area differfrom the rendering settings 30 in another mask area, what calculationmethod is applied to signal values of voxels on the projection rayvaries from one mask area to another. The resultant problem is thatrendering cannot be executed unless the collision between calculationmethods is dealt with.

The medical image display device 1 of this embodiment therefore performssome priority processing on each rendering element 35 before rendering.The priority processing here is processing of changing the compositiverendering element 43 based on priority in order to avoid the collisionbetween calculation methods described above. To give a more detaileddescription, the priority processing is processing of changing maskareas or rendering parameters based on priority in order to avoid acollision between rendering methods or rendering parameters on aprojection ray.

To execute this priority processing, a priority order 42 is attached tothe rendering element 35 and information of a priority processing method41 is attached to the compositive rendering element 43. The priorityprocessing method 41 is information that defines a priority processingmethod to be applied, and may define priority processing individuallyfor every combination of rendering elements, or may define, for eachrendering element, priority processing for all rendering elements belowthe rendering element in question at once. The priority processingmethod 41 may specify one particular priority processing method, or mayinclude all methods that can be selected as candidates so that a usercan choose one of the candidates. In this embodiment, extended areaexcluding processing, area excluding processing, or rendering parameterintegrating processing is defined as the priority processing method 41.Details of these priority processing methods 41 are described later.

The priority order 42 and the priority processing method 41 may be setnot only to the compositive rendering element 43 but also to thecompositive rendering settings 40. In the case where the compositiverendering element 43 is configured by allocating the rendering target 36to the compositive rendering settings 40 to which the priority order 42and the priority processing method 41 are attached, the priority order42 and priority processing method 41 of the compositive renderingsettings 40 may be used for the compositive rendering element 43 as theyare, or may be modified before being used for the compositive renderingelement 43.

In the case where a plurality of three-dimensional data names 37included in the compositive rendering element 43 differ from oneanother, the priority processing described above is executed afterpositioning in the three-dimensional space. Possible cases where onethree-dimensional data name 37 included differs from another are whenthe compositive rendering element 43 includes pieces ofthree-dimensional data generated from images of the same subject thathave been taken at different times, when the compositive renderingelement 43 includes pieces of three-dimensional data generated fromimages that have been taken by different medical imaging machines 21,and the like.

Not all items that constitute these rendering settings 30, the renderingelement 35, the compositive rendering settings 40, and the compositiverendering element 43 need to be set. In the case where one of the itemsis not set, the item is treated as being in an initial state which isdefined in advance, or as being not set yet. The rendering settings 30may be treated as the compositive rendering settings 40 when only onerendering settings pattern 30 is included and the priority processingmethod 41 and the priority order 42 are not set. Similarly, therendering element 35 may be treated as the compositive rendering element43.

Described next with reference to FIG. 4 and FIG. 5 is an example of theflow of processing in which a user interprets a medical image with theuse of the medical image display device 1 according to this embodiment.The description given here has in mind as the user a radiologist who hasreceived a medical image interpretation order, or the like.

The input part 2 of the medical image display device 1 receives loginprocessing from the user, and the list management part 6 then executesuser authentication processing (S100). The list management part 6generates a list of medical image interpretation orders and the userselects information of an interpretation target (S102). The descriptiongiven here has in mind, as the interpretation target information, a setof sectional images collected by the medical imaging machine 21,three-dimensional data constructed in advance from the set of sectionalimages, a medical image rendered for three-dimensional data, thecompositive rendering element 43 which includes three-dimensional datanames, and the like. The interpretation target information may also beselected by the user by searching information that is accumulated in themedical information management server 15 with a patient name, a testname, an image set name, or the like as a key.

The communication part 4 transmits a data request that reflects theuser's selection to the medical information management server 15. Themedical information management server 15 searches the storage 18 forrequested information (namely, the interpretation target informationselected by the user), and transmits information that fits from thecommunication part 17 to the medical image display device 1. Thecommunication part 4 of the medical image display device 1 receives theinterpretation target information and, in the case where the informationis a set of sectional images, the rendering processing part 8 constructsthree-dimensional data from the set of sectional images, and accumulatesthe data in the storage 10 (S104).

The user next uses a compositive rendering element displaying area 52and a details setting area 55 of a screen 50 (see FIG. 5), which is keptby the display part 26, to set the compositive rendering element 43including at least one rendering element 35 that is a combination of therendering method 31, the rendering parameter 32, the three-dimensionaldata name 37 of the interpretation target, and the mask name 38 (S106).

The display control part 9 displays in the compositive rendering elementdisplaying area 52 a list of the rendering elements 35 that constitutethe compositive rendering element 43 set (or to be set or to be changed)by the user. The rendering elements 35 are allocated rows of the listfrom the top downward in accordance with their respective places inpriority order. Each row displays items that constitute the renderingelement 35. When the user selects a row or an item with an input devicesuch as a mouse, detailed information is displayed in a details settingarea 55 so that modifications can be made. For an item that has not beenset, a blank field or an indication that the item has not been set isdisplayed.

The compositive rendering element 43 may be set with the use of thecompositive rendering settings 40 that are saved in advance in thestorage 10 of the medical image display device 1 or the storage 18 ofthe medical information management server as settings patterns typicalfor different purposes of medical image interpretation. Alternatively,the compositive rendering element 43 may be set by using the compositiverendering settings 40 that have been selected as an initial value andmodifying the initial value. A new compositive rendering element 43 mayalso be created. The compositive rendering element 43 that includes thethree-dimensional data name 37 of the interpretation target may becalled and used to set the compositive rendering element 43. Thecompositive rendering settings 40, the compositive rendering element 43,and other types of information saved in the storage 10 of the medicalimage display device 1 or the storage 18 of the medical informationmanagement server are generated by the list management part 6 anddisplayed in a library area 54 in response to the user's request.

The rendering processing part 8 generates a mask specified by the maskname 38 by an arbitrary method, and saves the mask in the storage 10.Examples of the arbitrary method include a method in which all voxelsare set as a rendering target area, a method in which thresholdprocessing is performed on the signal value of each voxel, a method inwhich the user manually selects an area with the use of a renderedmedical image, a method in which an area growth method is used with apoint specified by the user as the starting point, and a method in whicha mask is called with the use of the mask name 38 of the renderingtarget 36 saved in the storage 10 of the medical image display device 1or the storage 18 of the medical information management server.

In the case of performing threshold processing on the signal value ofeach voxel, a mask is generated so that an area of voxels whose signalvalues are larger (or smaller) than a given threshold out of all voxelsis set as a rendering target area (namely, mask area). In the case wherethe user manually selects an area, a mask is generated so that the areaselected by the user is set as a rendering target area.

After the user sets the compositive rendering element 43, the renderingcontrol part 7 executes priority processing based on the compositiverendering element 43 (S108). The priority processing is described later(see FIG. 6). Next, the rendering processing part 8 renders an image(S110), and the generated medical image is displayed in an imagedisplaying area 51 of the screen 50 (S112). The user consults thedisplayed medical image to make a diagnosis, and operates the medicalimage display device 1 by specifying a region of interest (ROI),entering a comment, or the like (S114).

When there is a possibility that the set compositive rendering settings40, or the rendering settings 30 that constitute the set compositiverendering settings 40, might be reused for another piece of data, theuser specifies the compositive rendering settings 40 or the renderingsettings 30 to be reused in the compositive rendering element displayingarea 52. The rendering control part 7 saves the specified compositiverendering settings 40 or rendering settings 30 in the storage 10 of themedical image display device 1 or the storage 18 of the medicalinformation management server (S116 and S118). Similarly, when there isa possibility that the rendering result of this interpretation targetmight be reproduced later, the rendering control part 7 saves thecompositive rendering element 43 or the rendering elements 35 (S120 andS122).

Items constituting the compositive rendering element 43 can be modifiedafter the rendering processing as well. For instance, to make aplurality of types of diagnoses with the use of the samethree-dimensional data, the rendering control part 7 can modify thespecifics of the respective items of the compositive rendering element43 to suit the respective purposes of the diagnoses. In the case wheresuch modifications are made, the rendering processing is executed anewbased on the modified compositive rendering element 43, and thedisplayed image is updated (S124).

In the case where the user wishes to interpret a medical image ofanother piece of data, S102 and the subsequent steps are executed anew,thereby switching the target data and rendering a new image (S 126).

In the case where a medical image interpretation report needs to begenerated, the display control part 9 executes report generatingprocessing with the use of the medical image rendered, an ROI or commententered by the user, and the like (S128), registers the report in thestorage 18 of the medical information management server 15 (S130), andthen ends the medical image interpretation.

The priority processing (S 108) executed by the rendering control part 7is described next in detail with reference to FIG. 6.

After the user sets the compositive rendering element 43 (S106), therendering control part 7 checks the count of the rendering elements 35that are included in the set compositive rendering element 43 (S200).When one rendering element 35 is included, only one mask area is set andthere is no need to execute the priority processing. The renderingprocessing part 8 therefore renders an image (S110) without executingthe priority processing. In the case where the compositive renderingelement 43 includes two or more rendering elements 35, the renderingcontrol part 7 executes the priority processing as needed (S202 toS216).

The rendering control part 7 first determines whether or not thecompositive rendering element 43 includes the rendering element 35 forwhich the priority processing has not been performed (S202).Specifically, the rendering control part 7 determines, for eachrendering element 35, whether or not priority processing between therendering element 35 and the rendering elements 35 below the renderingelement 35 in question has been executed. This determination is madebased on the value of a priority processing flag, which is describedlater. When it is determined that priority processing between therendering element 35 and its lower rendering elements 35 has not beenexecuted with respect to at least one rendering element 35 (in otherwords, that the compositive rendering element 43 includes the renderingelement 35 for which the priority processing has not been performed),the rendering control part 7 selects one of those rendering elements 35that is highest in priority order (hereinafter referred to as renderingelement A) (S204). In the following description, a rendering elementthat is assigned a higher place in priority order may also be simplyreferred to upper rendering element, and a rendering element that isassigned a lower place in priority order may also simply referred to aslower rendering element.

The rendering control part 7 next determines whether or not thecompositive rendering element 43 includes the rendering element 35 thatis below the rendering element A and that has not been processed bypriority yielding processing (S206). Specifically, the rendering controlpart 7 determines, for each rendering element 35 below the renderingelement A, whether or not priority processing between the renderingelement 35 in question and the rendering element A (i.e., priorityyielding processing) has been executed. This determination is made basedon the value of a priority yielding processing flag, which is describedlater. When it is determined that the priority yielding processing hasnot been executed for at least one rendering element 35, the renderingcontrol part 7 selects one of those rendering elements 35 that ishighest in priority order (hereinafter referred to as rendering elementB) (S208).

The rendering control part 7 next selects a priority processing methodfor the two selected rendering elements 35 (i.e., the rendering elementA and the rendering element B) (S210). Specifically, in the case whereone priority processing method is defined in advance by the priorityprocessing method 41 of the compositive rendering element 43 for the twoselected rendering elements 35, the rendering control part 7 refers tothe defined method. In the case where a plurality of priority processingmethod candidates that can be selected are defined instead of onepriority processing method, on the other hand, a message prompting theuser to input is displayed. The user enters an instruction in which oneof the priority processing method candidates is chosen to the input part2.

The rendering control part 7 next executes the priority processing by apriority processing method that is selected for the rendering element B(S212), and sets “on” to the priority yielding processing flag of therendering element B.

After selecting and executing the priority processing in a similarmanner for every lower rendering element 35, the rendering control part7 sets “on” to the priority processing flag of the rendering element Aand sets “off” to the priority yielding processing flag of everyrendering element 35 below the rendering element A (S216). When thepriority processing flag of every rendering element 35 is “on”, therendering processing part 8 renders an image (S110).

The priority processing flag and the priority yielding processing flag(both are omitted from the drawings) are flags attached to eachrendering element 35, and are managed internally by the renderingcontrol part 7. The priority processing flag is a flag indicatingwhether or not priority processing between the rendering element 35 towhich the flag in question is attached and every rendering element 35below this rendering element 35 has been executed. A value “on” of thepriority processing flag indicates that the priority processing has beenexecuted. The priority yielding processing flag is a flag indicatingwhether or not priority processing between the rendering element 35 towhich the flag in question is attached and a particular renderingelement 35 above this rendering element 35 has been executed. A value“on” of the priority yielding processing flag indicates that thepriority processing has been executed.

The selection of a priority processing method (S210) is described nextwith reference to FIG. 7, FIGS. 8A to 8C, and FIGS. 9A and 9B. Thepriority processing requires taking into consideration a situation inwhich mask areas overlap in the direction of a projection ray 60 withwhich an image is rendered. Situations in which a mask area 62 of therendering element A high in priority order and a mask area 61 of therendering element B low in priority order overlap each other areclassified here into four patterns: one in which the two do not overlapand are not located on the same projection ray (in other words, noprojection ray 60 passes through the two mask areas) (FIG. 8A); one inwhich the two do not overlap and are located on the same projection ray(in other words, at least part of the projection ray 60 passes throughthe two mask areas) (FIG. 8B); one in which there is an overlapping area63 between the two (in other words, at least some of signal valuesbelonging to one of the mask areas belong to the other mask area aswell) (FIG. 8C); and one in which the two coincide with each othercompletely (in other words, the two mask areas overlap entirely) (notshown).

The selection of two rendering elements in FIG. 7 (S300) corresponds toS202 to S208 of FIG. 6. In the case where pieces of three-dimensionaldata, rendering methods, and rendering parameters of the two renderingelements all match (S302), rendering processing can be executed withoutperforming the priority processing whatever the mask area overlappingsituation is. It is therefore determined that executing the priorityprocessing is unnecessary (S316). The execution of the priorityprocessing is determined as unnecessary also when the two mask areas donot overlap and are not located on the same projection ray (FIG. 8A,S304 of FIG. 7) and there is accordingly no fear that a plurality ofrendering methods are applied on the same projection ray (in otherwords, no collision between a plurality of rendering methods or aplurality of rendering parameters) (S316).

In other cases than those described above, a collision occurs between aplurality of rendering methods or a plurality of rendering parameters,and needs to be avoided by executing the priority processing.

First, in the case where different rendering methods are applied (S306),the rendering control part 7 executes extended area excluding processingas the priority processing so that only one rendering method is appliedon the same projection ray. The extended area excluding processing isprocessing that is executed when two mask areas specified by the tworendering elements 35 are at least partially on the same projection rayto remove a portion on the same projection ray from one of the two maskareas that is specified by the lower rendering element 35. Morespecifically, the extended area excluding processing is processing ofremoving an area that is an extension of the mask area 62 of thehigh-priority rendering element A in a direction parallel to theprojection ray 60 (the area indicated by broken lines 66) from the maskarea 61 of the low-priority rendering element B, and setting theresultant area as a mask area 65 on which the priority yieldingprocessing of the rendering element B has been executed.

This mask area modification is executed by, for example, newly creatinginformation for specifying the mask area 65 and changing the mask name38 that is included in the rendering target 36 of the rendering elementB from the name of the mask area 61 to the name of the mask area 65. Thesame applies to area excluding processing, which is described later.

In the case where the priority processing is necessary and the two maskareas use different rendering methods, the extended area excludingprocessing is selected automatically. A collision between renderingmethods on a projection ray is thus solved.

In the case where the priority processing is necessary and the two maskareas use the same rendering method, the rendering control part 7chooses one of the extended area excluding processing described aboveand area excluding processing that suits the purpose (S310). The areaexcluding processing is processing that is executed when two mask areasspecified by the two rendering elements 35 overlap at least partially toremove the overlapping portion from one of the two mask areas that isspecified by the lower rendering element 35. More specifically, the areaexcluding processing is processing of removing an area that overlapswith the mask area 62 of the high-priority rendering element A from themask area 61 of the low-priority rendering element B, and setting theresultant area as a mask area 67 on which the priority yieldingprocessing of the low-priority rendering element B has been executed. Acollision between rendering parameters in an overlapping area is thussolved.

However, in the case where the priority processing is necessary, the twomask areas use the same rendering method, the two rendering elementshave the same three-dimensional data, and the mask areas overlap atleast partially (S308), a collision between rendering parameters in theoverlapping area 63 may be solved by selecting processing of integratingthe rendering parameters 32 for the overlapping area 63, instead of theextended area excluding processing and the area excluding processing(S312). The rendering parameter integrating processing is processingthat is executed when two mask areas specified by the two renderingelements 35 overlap at least partially to create a new renderingparameter by integrating the two rendering parameters 32 that areassociated with the mask areas, and to switch the rendering parameter ofthe overlapping area to the new rendering parameter. Details of therendering parameter integrating processing are described later (see FIG.10).

In the case where priority processing can be selected from a pluralityof candidates, the user chooses one that suits the purpose of diagnosisby taking into account what medical image is being requested. A medicalimage rendered by executing the extended area excluding processing doesnot have an overlapping area to which different rendering methods anddifferent rendering parameters are applied. The extended area excludingprocessing is therefore used when, for example, a particular area isdisplayed by VR rendering whereas other areas are displayed by MIPrendering.

The area excluding processing, on the other hand, is used when only asingle rendering settings pattern 30 is applied to each mask area. Inthe case where mask areas of respective rendering elements do notoverlap in a three-dimensional space but are on the same projection ray,an image is rendered by using both rendering settings during projectionprocessing. The area excluding processing is used when, for example, adifferent opacity curve is set for each mask area and the entire imageis rendered by VR.

The rendering parameter integrating processing is used when a pluralityof rendering elements have the same rendering method and differentrendering parameters, mask areas of the rendering elements coincide orat least partially overlap with one another, and rendering processing isexecuted by integrating the plurality of rendering parameters andapplying the resultant rendering parameter to the overlapping area. Thearea excluding processing and the extended area excluding processing arenot performed on the overlapping area in this case. Here, renderingparameters are integrated into one by removing a range of target valuesof the high-priority rendering element A from a range of target valuesof the low-priority rendering element B, and the resultant renderingparameter is applied to the overlapping area 63. The rendering parameterintegrating processing is used when, for example, an image is renderedby VR by selecting from the storage 10 a plurality of rendering settingspatterns that include opacity curves for displaying a particular site ororgan, allocating the rendering settings patterns to the respectiverendering elements, and rendering the whole image with an opacity curvethat is obtained through the integration of the rendering settingspatterns.

An example of using the rendering parameter integrating processing isdescribed in detail with reference to FIG. 10. The example used here isthe compositive rendering element 43 which includes a plurality ofrendering elements 35 that have the same three-dimensional data andrendering method (specifically, RV) and different masks and renderingparameters (specifically, opacity curves 73 and 75) from one another. VRis a rendering method in which pixel values on a screen are calculatedfor signal values of three-dimensional data on a projection ray bytaking into account the opacity, color, and light attenuation of signalvalues that are defined by an opacity curve in order from the forward.

Each rendering element 35 includes the specification of the range ofrendering target signal values (namely, the target value range 33). Theopacity curves 73 and 75 are modified so that, when mask areas of tworendering elements 35 overlap and the rendering target signal valueranges overlap in the overlapping area 63, the opacity curve 73specified by the rendering element 35 that is high in priority order isapplied in the overlapping signal value range, which is denoted by 77,whereas the opacity curve specified by one of the rendering elements 35(namely, the opacity curve 73 or 75) is applied to the other as well insignal value ranges that do not overlap.

Specifically, on opacity curves that have signal value on the axis ofabscissa, a value range 72 of the upper rendering element in priorityorder is removed from a value range 74 of the lower rendering element,to thereby eliminate the overlapping of value ranges, and an integratedopacity curve 78 is generated by integrating the opacity curves 73 and75 in the respective value ranges. In the area where the masks overlap,calculation processing of VR is executed with the integrated opacitycurve 78, instead of the opacity curve 73 or 75, and the opacity curves73 and 75 set by the respective rendering elements are used in areaswhere the masks do not overlap to execute calculation processing of VR.

An opacity curve is set, for example, as follows. The user chooses aparticular rendering element out of rendering elements displayed in thecompositive rendering element displaying area 52 of the screen 50. Therendering control part 7 then displays in the details setting area 55 anopacity curve that is included in the chosen rendering element. The usermay select a plurality of rendering elements in the compositiverendering element displaying area 52 so that the integrated opacitycurve 78 is displayed.

Processing of excluding a value range is executed as rendering parameterintegrating processing in the example described above. Other methods maybe used to integrate rendering parameters, such as an alpha blendingmethod in which coefficients associated with places in priority orderare allocated, or a method in which the parameter larger in opacityvalue is used in the case of opacity and the parameter higher inpriority order is used in the case of color.

While three types of priority processing, the extended area excludingprocessing, the area excluding processing, and the rendering parameterintegrating processing, are used here, other priority processing methodsthan these may be defined.

Described next with reference to FIGS. 11A to 11D is a method of showingto the user how much a rendering element that is low in priority ordercontributes in a two-dimensional image that is obtained as a result ofrendering processing when priority processing is executed.

The screen 50 of the display part 3 includes the image displaying area51 for displaying a rendered medical image and the compositive renderingelement displaying area 52 for displaying a compositive renderingelement. In the compositive rendering element displaying area 52, thedisplay control part 9 displays a list of the rendering elements 35 thatare included in the set compositive rendering element 43. For instance,one row of a table displayed in the compositive rendering elementdisplaying area 52 corresponds to one rendering element 35. A column 56having a checkbox or toggle button for switching “on” and “off” ofvisibility is placed in the rows of the rendering elements 35. When theuser uses this to set “on” to the visibility of a particular renderingelement 35 alone and set “off” to the visibility of the other renderingelements 35, the rendering processing part 8 displays only the renderingresult of an area to which the particular rendering element 35contributes in the image displaying area 51.

A column 57 having a checkbox or toggle button for switching “on” and“off” of the enabled state is placed in the case where a differencebetween rendering results due to whether the priority processing isexecuted or not is to be visualized. When the user uses this to set “on”to the enabled state of a particular rendering element 35 alone and“off” to the enabled state of the rendering elements 35 above theparticular rendering element 35, priority processing between theparticular rendering element 35 and its upper rendering elements 35(namely, modifications to mask areas or rendering parameters) iscancelled. A rendering result of the particular rendering element thathas not been influenced by the priority processing is thus displayed bythe rendering processing part 8.

For instance, when the user inputs an instruction to change thevisibility or enabled state of one of the rendering elements 35, therendering control part 7 may modify the compositive rendering element 43following the input instruction (S 124) and execute priority processingbased on the modified compositive rendering element 43 (S108), and therendering processing part 8 may render an image on which the priorityprocessing is reflected.

FIG. 11A illustrates areas 80 and 81 which are the projection onto atwo-dimensional image 82 of masks set by two rendering elements, therendering element A high in priority order and the rendering element Blow in priority order. In the case where the extended area excludingprocessing is chosen as priority processing for the two renderingelements, an area is removed from the mask area 81 of the renderingelement B which overlaps with an area that is an extension of the maskarea 80 of the rendering element A in a direction parallel to theprojection ray (i.e., a direction orthogonal to the screen of thetwo-dimensional image 82) as illustrated in FIG. 11B. This makes therendering range of the rendering element B an area 83, which is theprojection of a mask processed by the priority yielding processing ontothe two-dimensional image. In the case where “off” is set to thevisibility of the rendering element A and “on” is set to the visibilityof the rendering element B at this point, only the area 83 is displayedas illustrated in FIG. 11C. In the case where “off” is set to theenabled state of the rendering element A at this point, the area 81 inwhich priority processing is not performed is displayed as illustratedin FIG. 11D.

The influence on a particular rendering element can similarly be shownto the user also when other types of priority processing are selected.The order of the rendering elements 35 on the list of the renderingelements 35 can be changed in the compositive rendering elementdisplaying area 52. After the rendering elements 35 switch their placesin order, the rendering control part 7 executes the priority processingagain and the rendering processing part 8 updates the displayed image.

Described next with reference to FIG. 5 is a method of showing to theuser a rendering element that is involved in rendering with respect toeach pixel in a medical image generated by rendering processing. Whenthe user clicks on a particular pixel in the image displaying area 51 ofthe screen 50 with the use of an input device such as a mouse, therendering control part 7 displays a row 58 of a rendering element thatis involved in the rendering of the pixel in an emphasized manner in thecompositive rendering element displaying area 52. The emphasized displayis accomplished by, for example, changing the color of the row 58,displaying a frame that surrounds the row 58, or displaying an icon thatrepresents emphasis.

For instance, the rendering control part 7 may identify a mask areawhere a projection ray that reaches the pixel specified by the userpasses through, and identify the rendering element 35 that is associatedwith the mask area (i.e., the rendering element 35 that includes themask name 38 by which the mask area is specified) as a rendering elementthat is involved in the rendering of the pixel. The rendering controlpart 7 instructs the display part 3 to display the identified renderingelement in an emphasized manner, and the display part 3 displays theidentified rendering element in an emphasized manner following theinstruction.

This method enables the user who is viewing a displayed two-dimensionalimage in order to modify a rendering element to easily find out whichrendering element is to be modified.

The program that implements the functions, tables, files, and othertypes of information can be stored in a storage device such as anon-volatile semiconductor memory, a hard disk drive, or a solid statedrive (SSD), or a computer-readable non-transitory data storage mediumsuch as an IC card, an SD card, or a DVD.

This invention is not limited to the embodiment described above, andencompasses various modification examples. For instance, the embodimenthas described this invention in detail for the ease of understanding,and this invention is not necessarily limited to a mode that includesall of the configuration described above. A part of the configuration ofone embodiment may be replaced with the configuration of anotherembodiment, and the configuration of one embodiment may be used incombination with the configuration of another embodiment. In eachembodiment, another configuration may be added to, deleted from orreplace a part of the configuration of the embodiment.

What is claimed is:
 1. An image display device, comprising: a firstcontrol part; a first storage; and a display part, wherein the firststorage holds a plurality of rendering elements each of which comprisesa combination of rendering target information, which specifies arendering target, and rendering settings information, which is referredto when the rendering target is rendered, and holds a place in priorityorder assigned to each of the plurality of rendering elements, whereinthe rendering target information comprises data identificationinformation for specifying three-dimensional arrangement of signalvalues which are rendering targets, and mask information for specifyinga rendering target area out of the three-dimensional signal valuearrangement, wherein the rendering settings information comprisesinformation for specifying a method of rendering a two-dimensional imagebased on the three-dimensional signal value arrangement, and informationfor specifying a rendering parameter to be applied to the renderingmethod, wherein the first control part is configured to: determine,based on the rendering settings information and the mask information,whether or not priority processing in which one of the mask informationor the rendering parameter is modified needs to be executed; modify,when it is determined that the priority processing needs to be executed,the one of the mask information or the rendering parameter; and render atwo-dimensional image based on the plurality of rendering elements thatcomprise the modified one of the mask information or the renderingparameter, and wherein the display part displays the two-dimensionalimage rendered.
 2. The image display device according to claim 1,wherein the priority processing comprises one of first priorityprocessing, second priority processing, or third priority processing,the first priority processing comprising removing, from the target areathat is lower in priority order out of two target areas that are atleast partially on the same projection ray, a portion that is on thesame projection ray, the second priority processing comprising removing,from the target area that is lower in priority order out of two targetareas that at least partially overlap with each other, the overlappingportion, the third priority processing comprising creating a newrendering parameter by integrating two rendering parameters that arecomprised in two rendering elements associated with two target areasthat at least partially overlap with each other, and at least partiallyswitching the two rendering parameters that are comprised in the tworendering elements to the new rendering parameter.
 3. The image displaydevice according to claim 2, wherein the first control part isconfigured to: determine that the priority processing does not need tobe executed for two rendering elements out of the plurality of renderingelements when two pieces of the rendering target information that arecomprised in the two rendering elements specify the samethree-dimensional signal value arrangement, two pieces of the renderingsettings information that are comprised in the two rendering elementsspecify the same rendering method, and the two pieces of the renderingsettings information specify the same rendering parameter; determine, atleast one of when the two pieces of the rendering target information donot specify the same three-dimensional signal value arrangement, whenthe two pieces of the rendering settings information do not specify thesame rendering method, or when the two pieces of the rendering settingsinformation do not specify the same rendering parameter, whether or nottwo target areas specified by the two pieces of the rendering targetinformation are on the same projection ray; determine, when the twotarget areas specified by the two pieces of the rendering targetinformation are not on the same projection ray, that the priorityprocessing does not need to be executed for the two rendering elements;and determine, when the two target areas specified by the two pieces ofthe rendering target information are on the same projection ray, thatthe priority processing needs to be executed for the two renderingelements, and wherein, when it is determined that the priorityprocessing needs to be executed, the first control part is configuredto: execute the first priority processing for the two rendering elementswhen the two pieces of the rendering settings information comprised inthe two rendering elements do not specify the same rendering method;execute one of the first priority processing, the second priorityprocessing, and the third priority processing for the two renderingelements when the two pieces of the rendering target informationcomprised in the two rendering elements specify the samethree-dimensional signal value arrangement, and the target areasspecified by the two pieces of the rendering target information overlapwith each other; and execute one of the first priority processing andthe second priority processing for the two rendering elements at leastone of when the two pieces of the rendering target information comprisedin the two rendering elements do not specify the same three-dimensionalsignal value arrangement, or when the target areas specified by the twopieces of the rendering target information comprised in the tworendering elements do not overlap with each other.
 4. The image displaydevice according to claim 3, wherein, when the rendering methodsspecified by the two pieces of rendering settings information that arecomprised in the two rendering elements are both volume rendering, therendering parameter specified by one of the two rendering elements thatis higher in priority order comprises first opacity information, whichspecifies at least one of opacity and color to be allocated to thesignals values in a first range, the rendering parameter specified byone of the two rendering elements that is lower in priority ordercomprises second opacity information, which specifies at least one ofopacity and color to be allocated to the signals values in a secondrange, and the third priority processing comprises processing thatinvolves 1) creating third opacity information for allocating the firstopacity information to a range where the first range and the secondrange overlap each other, for allocating the first opacity informationto a range where the first range does not overlap with the second range,and for allocating the second opacity information to a range where thesecond range does not overlap with the first range, and 2) switching thefirst opacity information and the second opacity information to thethird opacity information in a portion where the two mask areas overlapwith each other.
 5. The image display device according to claim 2,wherein the first control part is configured to: render, when aninstruction to disable visibility is input for one of the plurality ofrendering elements after the two-dimensional image is rendered based onthe plurality of rendering elements that comprise the modified one ofthe mask information or the rendering parameter, a two-dimensional imagebased on the signal values within a target area that is specified byother rendering elements than the one of the plurality of renderingelements for which the instruction has been input, without rendering animage based on the signal values within a target area that is specifiedby the one of the plurality of rendering elements for which theinstruction has been input; and cancel, when an instruction to disablean enabled state is input for one of the plurality of rendering elementsafter the two-dimensional image is rendered based on the plurality ofrendering elements that comprise the modified one of the maskinformation or the rendering parameter, one of the modification of themask information or the modification of the rendering parameter throughthe priority processing between the one of the plurality of renderingelements for which the instruction has been input and another renderingelement, and render a two-dimensional image based on the one of theplurality of rendering elements for which the modification has beencancelled.
 6. The image display device according to claim 1, wherein,when specification is input to specify one of pixels which are comprisedin the two-dimensional image rendered, the first control part displays,on the display part, information identifying one of the plurality ofrendering elements that is involved in rendering of the specified one ofthe pixels.
 7. The image display device according to claim 6, whereinthe first control part identifies, as the one of the plurality ofrendering elements that is involved in the rendering of the specifiedone of the pixels, one of the plurality of rendering elements that isassociated with the target area where a projection ray reaching thespecified one of the pixels passes through, and wherein the display partfurther displays a list of the plurality of rendering elements that hasbeen referred to in order to render the two-dimensional image, andwherein, out of the list of the plurality of rendering elements, thedisplay part displays items that are associated with the identified oneof the plurality of rendering elements in an emphasized manner,following an instruction from the first control part.
 8. An imagedisplay system, comprising: the image display device of claim 1; anetwork which is coupled to the image display device; and an informationmanagement server which is coupled to the network, wherein the imagedisplay device further comprises a first communication part which iscoupled to the network, wherein the information management servercomprises a second communication part, which is coupled to the network,a second control part, and a second storage, wherein the second storageholds at least one of 1) a set that comprises a plurality ofcombinations of the data identification information and the maskinformation, a plurality of combinations of the information forspecifying the rendering method and the information for specifying therendering parameter, a plurality of combinations of the rendering targetinformation and the rendering settings information, and a plurality ofcombinations of one rendering element and the place in priority order,and 2) a set that comprises a plurality of combinations of the renderingsettings information and the place in priority order, and wherein theimage display device stores, in the first storage, the plurality ofrendering elements and the places in priority order assigned to theplurality of respective rendering elements, based on information readout of the second storage.
 9. An image display method to be executed byan image display device, the image display device comprising: a firstcontrol part; a first storage; and a display part, the first storageholding a plurality of rendering elements each of which comprises acombination of rendering target information, which specifies a renderingtarget, and rendering settings information, which is referred to whenthe rendering target is rendered, and holding a place in priority orderassigned to each of the plurality of rendering elements, the renderingtarget information comprising data identification information forspecifying three-dimensional arrangement of signal values which arerendering targets, and mask information for specifying a renderingtarget area out of the three-dimensional signal value arrangement, therendering settings information comprising information for specifying amethod of rendering a two-dimensional image based on thethree-dimensional signal value arrangement, and information forspecifying a rendering parameter to be applied to the rendering method,the image display method comprising: a first procedure of determining,based on the rendering settings information and the mask informationwhether or not priority processing in which one of the mask informationor the rendering parameter is modified needs to be executed; a secondprocedure of modifying, when it is determined that the priorityprocessing needs to be executed, the one of the mask information or therendering parameter; a third procedure of rendering a two-dimensionalimage based on the plurality of rendering elements that comprise themodified one of the mask information or the rendering parameter; and afourth procedure of displaying the two-dimensional image rendered. 10.The image display method according to claim 9, wherein the priorityprocessing comprises one of first priority processing, second priorityprocessing, or third priority processing, the first priority processingcomprising removing, from the target area that is lower in priorityorder out of two target areas that are at least partially on the sameprojection ray, a portion that is on the same projection ray, the secondpriority processing comprising removing, from the target area that islower in priority order out of two target areas that at least partiallyoverlap with each other, the overlapping portion, the third priorityprocessing comprising creating a new rendering parameter by integratingtwo rendering parameters that are comprised in two rendering elementsassociated with two target areas that at least partially overlap witheach other, and at least partially switching the two renderingparameters that are comprised in the two rendering elements to the newrendering parameter.
 11. The image display method according to claim 10,wherein the first procedure comprises: determining that the priorityprocessing does not need to be executed for two rendering elements outof the plurality of rendering elements when two pieces of the renderingtarget information that are comprised in the two rendering elementsspecify the same three-dimensional signal value arrangement, two piecesof the rendering settings information that are comprised in the tworendering elements specify the same rendering method, and the two piecesof the rendering settings information specify the same renderingparameter; determining, at least one of when the two pieces of therendering target information do not specify the same three-dimensionalsignal value arrangement, when the two pieces of the rendering settingsinformation do not specify the same rendering method, or when the twopieces of the rendering settings information do not specify the samerendering parameter, whether or not two target areas specified by thetwo pieces of the rendering target information are on the sameprojection ray; determining, when the two target areas specified by thetwo pieces of the rendering target information are not on the sameprojection ray, that the priority processing does not need to beexecuted for the two rendering elements; and determining, when the twotarget areas specified by the two pieces of the rendering targetinformation are on the same projection ray, that the priority processingneeds to be executed for the two rendering elements, and wherein thesecond procedure comprises: executing the first priority processing forthe two rendering elements when the two pieces of the rendering settingsinformation comprised in the two rendering elements do not specify thesame rendering method; executing one of the first priority processing,the second priority processing, and the third priority processing forthe two rendering elements when the two pieces of the rendering targetinformation comprised in the two rendering elements specify the samethree-dimensional signal value arrangement, and the target areasspecified by the two pieces of the rendering target information overlapwith each other; and executing one of the first priority processing andthe second priority processing for the two rendering elements at leastone of when the two pieces of the rendering target information comprisedin the two rendering elements do not specify the same three-dimensionalsignal value arrangement, or when the target areas specified by the twopieces of the rendering target information comprised in the tworendering elements do not overlap with each other.
 12. The image displaymethod according to claim 11, wherein, when the rendering methodsspecified by the two pieces of rendering settings information that arecomprised in the two rendering elements are both volume rendering, therendering parameter specified by one of the two rendering elements thatis higher in priority order comprises first opacity information, whichspecifies at least one of opacity and color to be allocated to thesignals values in a first range, the rendering parameter specified byone of the two rendering elements that is lower in priority ordercomprises second opacity information, which specifies at least one ofopacity and color to be allocated to the signals values in a secondrange, and the third priority processing comprises processing thatinvolves 1) creating third opacity information for allocating the firstopacity information to a range where the first range and the secondrange overlap each other, for allocating the first opacity informationto a range where the first range does not overlap with the second range,and for allocating the second opacity information to a range where thesecond range does not overlap with the first range, and 2) switching thefirst opacity information and the second opacity information to thethird opacity information in a portion where the two mask areas overlapwith each other.
 13. The image display method according to claim 10,further comprising: rendering, when an instruction to disable visibilityis input for one of the plurality of rendering elements after thetwo-dimensional image is rendered based on the plurality of renderingelements that comprise the modified one of the mask information or therendering parameter, a two-dimensional image based on the signal valueswithin a target area that is specified by other rendering elements thanthe one of the plurality of rendering elements for which the instructionhas been input, without rendering an image based on the signal valueswithin a target area that is specified by the one of the plurality ofrendering elements for which the instruction has been input; andcanceling, when an instruction to disable an enabled state is input forone of the plurality of rendering elements after the two-dimensionalimage is rendered based on the plurality of rendering elements thatcomprise the modified one of the mask information or the renderingparameter, one of the modification of the mask information or themodification of the rendering parameter through the priority processingbetween the one of the plurality of rendering elements for which theinstruction has been input and another rendering element, and renderinga two-dimensional image based on the one of the plurality of renderingelements for which the modification has been cancelled.
 14. The imagedisplay method according to claim 9, further comprising a fifthprocedure of displaying, when specification is input to specify one ofpixels which are comprised in the two-dimensional image rendered, on thedisplay part, information identifying one of the plurality of renderingelements that is involved in rendering of the specified one of thepixels.
 15. The image display method according to claim 14, wherein thefifth procedure comprises: identifying, as the one of the plurality ofrendering elements that is involved in the rendering of the specifiedone of the pixels, one of the plurality of rendering elements that isassociated with the target area where a projection ray reaching thespecified one of the pixels passes through; displaying a list of theplurality of rendering elements that has been referred to in order torender the two-dimensional image; and displaying, out of the list of theplurality of rendering elements, items that are associated with theidentified one of the plurality of rendering elements in an emphasizedmanner.
 16. The image display method according to claim 9, wherein theimage display device has a network coupled thereto, wherein the networkhas an information management server coupled thereto, wherein the imagedisplay device further comprises a first communication part which iscoupled to the network, wherein the information management servercomprises a second communication part, which is coupled to the network,a second control part, and a second storage, wherein the second storageholds at least one of 1) a set that comprises a plurality ofcombinations of the data identification information and the maskinformation, a plurality of combinations of the information forspecifying the rendering method and the information for specifying therendering parameter, a plurality of combinations of the rendering targetinformation and the rendering settings information, and a plurality ofcombinations of one rendering element and the place in priority order,and 2) a set that comprises a plurality of combinations of the renderingsettings information and the place in priority order, and wherein theimage display method further comprises storing, in the first storage,the plurality of rendering elements and the places in priority orderassigned to the plurality of respective rendering elements, based oninformation read out of the second storage.